Radio resistor



Oct. '16, 1934. w, F, STEENWEG RADIO RES ISTOR Original Filed Sept. 6, 1929 Patented Oct. 16, 1934 UNITED STATES PATENT OFFICE RADIO RESISTOR consin Application September 6, 1929, Serial No. 390,836 Renewed January 24, 1934 Claims.

This invention relates to certain new and useful improvements in ignition circuits of automotive vehicles and refers more particularly to means for eliminating the interference produced 5 by the discharge of current across the spark plugs and affecting the reception of a receiver mounted within the vehicle.

In any electric network, an abrupt change in any of the circuit constants sets up an electromagnetic wave capable of afiecting radio receivers if the circuitconstants are appropriate, or, in other words, a sudden change of capacity, of inductance or resistance or the opening or closing of a circuit breaker in the network will set up an electro-magnetic wave if the circuit constants have the correct relationship. Hence, the discharge of current through the spark plugs or electric circuits of an automotive vehicle which is controlled by a circuit breaker sets up oscillations. These oscillations, although diminishing, continue after the initial surge, producing an electro-magnetic wave which will affect a radio receiver mounted within the vehicle, resulting in interference. These undesirable oscillations may be eliminated by the-adding of a resistance.

In carrying out the elimination of radio interference by this method, my invention has as one of its objects the provision of a resistor unit which is practical and conveniently adapted to automotive vehicles of all makes.

Another object of this invention resides in the provision of a resistor unit for the purpose described which is directly carried by the spark plugs, being either built therein or detachable therefrom.

A further object of this invention resides in the novel construction of the resistor units wherein a tubular resistance element is mounted between end terminals.

And a more specific object of this invention resides in the provision of a resistor unit adapted to be mounted upon a spark plug or integral therewith and in which means are provided for readily detachably connecting a conductor wire thereto whereby the current to the spark plug passes through the resistor element.

With the above and other objects in view which will appear as the description proceeds, my

invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

In the accompanying drawing, I have illustrated several complete examples of the physical embodiment of my invention constructed accord ing to the best modes I have so far devised for the practical application of the principles thereof, and in which:

Figure 1 is an elevational view of a portion of a spark plug illustrating my improved resistance element applied thereto, parts being broken away and in section.

Figure 2 is a similar view illustrating a slightly modified form of my invention.

Figure 3 is a transverse sectional view taken through a spark plug having a resistor element formed integrally therewith; and

Figure 4 is a diagrammatical view illustrating a conventional ignition circuit of an automotive vehicle equipped with my improved resistor element.

Referring now more particularly to the accompanying drawing, the numeral 5 represents a spark plug of conventional construction having a porcelain member 6 in which the center contact of the plug is axially embedded to be connected at its upper end with a threaded stud 7 adapted to receive one terminal '8 of the improved resistor unit, indicated generally as at 9.

The resistor unit comprises a tubular resistance element 10 moulded of a composition of a phenal condensation product, a filler and a conductor in the proportions to provide the desired conductive characteristics. The terminal 8 is secured to one end of the resistor unit in intimate contact with the adjacent end of the resistance element and a second terminal 11, similar to terminal 8, is likewise secured at the other end of the resistance element, the terminals each having a central projection 12 to snugly engage the bore 13 of the unit. The innermost ends of the projection 12 are reduced and provided with annular grooves 14, which with the remaining space within the resistance element are completely filled with a binding cement C composed essentially of asbestos and a phenol composition prodnot, which being an insulating composition does not in any way affect the resistance value of the element 10, but serves to maintain the terminals 8 and 11 in intimate contact with its ends.

Each terminal has an internally threaded aperture 15, the aperture of the terminal 8 receiving the threaded stud of the spark plug and the aperture of the terminal 11 receiving the threaded end of a screw 16 by which the terminal 17 of a con- 7'' ductor wire 18 may be readily detachably connected with the terminal 11 and thus with the spark plug center contact through the resistance element 10.

In Figure 2 a modified manner of constructing and mounting the resistor unit is illustrated. In this instance, the tubular resistance element 10 is somewhat shorter and larger in diameter and the terminals 8 and 11 are replaced by termina1s19 and 20. The terminal 19 consists of a metal washer having a central instruck portion 21 received in the bore of the unit to maintain the same against shifting, and is held in intimate engagement with the adjacent end of the resistance element by a screw 22. The screw 22 extends through axial apertures formed in an insulating member 23 of a diameter substantially equal to that ,of the resistance element and in engagement with the outer face of the terminal 20 which is apertured to substantially the same size as the bore of the resistance element and through an aperture in the central instruck portion of the washer forming the terminal member 19, to have a nut member 24 threaded thereon which binds the elements together and thus maintains the contacts 19 and 20 in intimate engagement with the ends of the resistance element. As clearly illustrated, the nut member 24 is in the form of a conventional terminalwith which a socket at the end of the conductor wire not. shown may be readily attached and detached.

The terminal 2Q-is preferably formed of bendable metal in the shape of a right-angular bracket having a horizontal arm 25 and a vertical arm 26. The vertical arm 26 has the resistance element secured thereto in the manner described and to prevent shifting of the resistance element thereon its outer face is counterbored, as at 27 to receive the outer diameter of the resistance element, and tongues 28 are struck rearwardly at spaced intervals to engage the insulating member 23 and I maintain the same against shifting. The hori-' zontal arm 25 of the bracket member is apertured to receive the screw threaded stud '7 projecting from the spark plug where it is secured by a nut 29 threaded thereon.

The resistor unit may also be formed integral with the spark plug as illustrated in' Figure 3, wherein the center contact 30 which is embedded in 'the porcelain member 6 of the plug extends upwardly therefrom to be received in the terminal 31 of a resistor unit 32 similar in construction to that illustrated in Figure 1. The end of the center. contact 30 may be secured in the terminal 31 in any desired manner and as the lower portion of the resistor unit 32 is embedded in the upper end of the porcelain member 6, it is obvious that the terminal 31 will be maintained in connection with the center contact 30. As stated, the construction of the unit 32 is similar to the modification illustrated in Figure 1, with the exception of the specific construction of the terminal 31. Figure 4 illustrates a conventional ignition circuit in which the battery 34, upon closing of an ignition switch 35, is connected with a circuit breaker 36, the stationary terminal of which is connected with the primary of an induction coil 37. The secondary'of the induction coil 37 as is customary is connected with the distributor arm 38 which cooperates with terminals 39 to select the spark plug to be fired. From the terminals 39 the conductors 18. lead to the terminals 11 of the resistor units which are mounted on the spark plugs so that the current must pass through the resistance before reaching the plugs. A resistance element 40 is also placed in series between the opposite end of the secondary of the induction coil and the ground, the value of which isgpreferably the same as that at the different spark plugs which has been found for most instances to be approximately 25,000 ohms.

From the foregoing description taken in connection with the accompanying drawing it will be readily apparent to those skilled in the art to which my invention appertains that I provide an eflicient and practical method of eliminating undesirable oscillations usually found in an ignition circuit and which if unprevented produce excessive interference with radio reception by a receiver located within the vehicle.

It is also apparent that this invention provides a novel resistor unit constructibn, which, while particularly adapted for use in connection with a spark plug for the purpose set forth, is also susceptible to general use.

While the modification shown in Fig. 3 is de-- scribed in substantial detail, it is'not claimed in the instant application, as it forms the subject matter of a divisional application, Serial ,No. 612,412 filed May 20, 1932.

What I claim as my invention is:

1. A device for eliminating radio interference arising from the discharge of the spark plug of an internal combustion engine, comprising a tubular electrical resistor element molded of materials having a high degree of electrical resistance, end terminals at the ends of the resistor element and having portions thereof projected into the bore of the tubular member, non-conducting material filling the bore of the tubular member and engaging the portions of the end'terminals projected therein to maintain the terminals in intimate contact with the ends of the resistor element, means for connecting one of the end terminals with the spark plug terminal, and means for connecting a conductor wire with the other end terminal.

2. A- resistor unit comprising a tubular electrical resistor element molded of materials having a high degree of electrical resistance, end terminals at the ends of the resistor element and having portions thereof projected into the bore of the tubular element, and non-conducting material filling the bore of the tubular element and engaging the portions of the end terminals projected therein to maintain the elements in intimate contact with the ends of the tubular resistor element, said end terminals having means for the connection of electrical conductors thereto.

3. A resistor unit of the character described comprising, a self-supporting tubular electrical resistor element, end terminals at the ends of said element, means carried by said end terminals and projected into the bore of said element, non-conducting material filling the bore of said element and firmly engaging said means projected thereinto from the end terminals to maintain the end terminals in intimate contact with the ends of the resistor element, and said end terminals having means for the connection of electrical conductors thereto.

4. A resistor unit comprising, a selfsupporting tubular electrical resistor body, end terminals at the ends of said resistor body, serrated projections formed" on the end terminals and extending into the bore of the resistor body, non-conducting cementitious material filling the bore of the resistor body and engaging the serrated projections to maintain the end terminals in intimate contact with the ends of the resistor body,' said end terminals having ngeans for the connection of electrical conductors thereto.

5. A resistor unit of the character described,

comprising a hollow cylinder molded of materials having a high degree of electrical resistance, terminals for the ends of the hollow cylinder each having a face-to-face contact with its respective end of the cylinder, projections formed on the terminals and extending into the hollow cylinder with a portion in direct engagement with the internal wall of the cylinder and an undercut 

